The dithiane 11 is alkylated with prenyl bromide to give 12. Hydrogenolysis of 12 with Raney-Nickel yields α-curcumene (6), hydrolysis of 12 gives the ketone 13. Prenal dithiane (14) is alkylated with 8 to give 15. ar-Turmerone (16) is formed by hydrolysis of 15. Reaction of 15 with sodium in liquid ammonia leads to a mixture of α-curcumene (6) and β-curcumene (10).